Various aspects of the present invention relate to electronic writing systems and, moreover, to eraser assemblies for electronic writing systems.
It is known to digitize handwriting on a surface, such as a piece of paper, by determining how a pen is moved. A position-coding pattern for coding coordinates of points can be provided on the surface. The pen can be provided with a sensor for recording the position-coding pattern locally at the tip of the pen as the pen is moved across the surface. A processing unit, which can be placed in the pen or at a distance therefrom, can decode the recorded position-coding pattern by analyzing the portion of the pattern viewed by the sensing device. As a result, movement of the pen across the surface can be determined as a series of coordinates.
For example, there exists a method of determining coordinates from a dot pattern on a piece of paper. Each set of six-by-six dots accurately defines a single coordinate. A pen containing a sensing device can view the dots and, thereby, calculate the coordinate at which the pen is positioned. For example, International Patent Publication No. WO 01/26032 and U.S. Pat. No. 7,249,716 describe such dot patterns.
Conventional electronic whiteboard systems do not currently implement dot patterns.
Conventional electronic whiteboard systems do, however, provide erasers for erasing digital markings of a pen or stylus. But currently, electronic erasers for such systems come with a number of disadvantages.
Rectangular erasers are provided for conventional non-electronic whiteboards. Rectangular erasers are beneficial because they allow a user to erase either a large swath or a smaller portion with a single stroke, depending on how the eraser is oriented in the plane of the whiteboard surface.
On the other hand, electronic whiteboard systems generally implement circular erasers. Rectangular erasers, while beneficial, would require the electronic whiteboard system to determine the orientation as well as the placement of the eraser, as the area of erasure depends on both these variables. In contrast, orientation of a circular eraser is irrelevant because a circle covers the same space regardless of orientation. The user of an electronic whiteboard system with a circular eraser, however, may not be able to vary the size of the area erased in a single stroke.
With standard whiteboard erasers, the user can tip the eraser against the whiteboard surface, so that an angle greater than zero exists between the surface and the eraser pad. Tipping can result in erasure of an even smaller swath than can be otherwise erased. With most electronic whiteboards, however, tipping the eraser causes undesirable effects. For example, the whiteboard system may not recognize that erasure is desired, or may incorrectly determine the position, orientation, or both, of the eraser.